1. Field of the Invention
The present invention relates to a system for remotely measuring the thickness of vessel linings by using digital data imaging. The invention may be used to inspect and repair the interior of refractory-lined vessels or furnaces such as those used in metallurgical processing and other applications.
2. Description of Related Art
The walls of steel furnaces and other vessels used in steel and metal making are typically covered by refractory linings made of bricks. For example, a basic furnace (BOF) for steel making is typically formed from three shells: an inner working lining of bricks, a middle safety lining also of bricks, and an outer shell usually of steel. The inner and working linings together are usually about three feet thick. The working lining undergoes uncontrolled and unpredictable wear during steel processing. Consequently, in order to maintain safe and economical production rates, the linings must be periodically inspected to ascertain their remaining thickness.
Among the systems currently available for measuring the linings of such vessels are those described in U.S. Pat. No. 5,212,738 to Chande et al., and in U.S. Pat. No. 5,127,736 to Nehisel. Chande et al. teaches a laser scanning system that determines the thickness of an object, such as the interior of a furnace. The thickness is determined by first measuring the distance between the object and an imaging device (i.e., laser), and then comparing the measured distance with a predetermined mathematical model of the object.
Neiheisel teaches an apparatus that directs a continuous wave laser beam light at the refractory lining within a furnace vessel, and the displacement, as measured by a self-scanned linear array of the scattered light beam from a nominal or reference position, is measured to provide an indication of lining wear or damage. The video signal received by the linear array receiver provides information for mapping the worn or damaged areas of the vessel lining so that such areas may be repaired by a gunning spray nozzle operated manually.
Among the systems currently available for repairing the linings undergoing wear are those described in U.S. Pat. No. 4,107,244 to Ochiai et al. and U.S. Pat. No. 4,218,989 to Fujita et al. Ochiai et al. disclose a method for transmitting microwaves into the surface of a heated refractory lining in a vessel, detecting the waves reflected from the surface, detecting the difference between the reference surface of the refractory lining and the damaged surface from the phase difference of the microwaves, controlling the transfer of the refractory gunning nozzle inserted into the vessel with the use of the deviation signal, and making the lining repair in the hot atmosphere. The steps related to inspection of the vessel are carried out separately from the steps related to repair of the vessel.
Fujita et al. disclose an apparatus for applying refractory material that includes a TV camera at a desired position on a spray pipe and a monitoring device which is located outside of a furnace. The TV camera has a visual range directed towards the same direction as that of the spray nozzle, so that an operator of the spray nozzle can accordingly conduct a considerably accurate and safe lining operation.
The present invention represents an improvement over the systems in the prior art in that it is an automated solution to the problem of inspecting and repairing vessels, and thus, does not require the supervision of a human operator at the time of repair. Further, the present invention does not require the use of programmable logic controllers (PLCs) as part of the repair mechanism. Further, the inspection mechanism of the present invention does not require the use of each and every coordinate or point in space that is read from a point cloud reflected from the interior of the vessel. Still further, the present invention incorporates a numerical controller for controlling the refractory material spray gun, which allows for precise spraying of the repair material and thus avoids waste of the material and saves time. Finally, the image of the interior of a vessel is produced in 3-D (as opposed to 2xc2xdD) which also enables the precise spraying of the material, thus saving time.
Methods and systems for inspecting and repairing vessel systems are disclosed. Specifically, such methods and systems include a laser used to project laser light into a hot furnace or vessel, a laser reader to measure a point cloud formed when the laser light reflects from the wall of the furnace, means for selecting those points in the cloud that are more relevant, and using the points to produce a 3D image that corresponds to the geometry of the interior of the furnace or vessel.
Such systems and methods further include means for comparing the 3D geometric data corresponding to the interior of the vessel with 3D geometric data provided as a reference, generating a 3D repair trace based on the comparison, and controlling a spray gun for applying refractory material according to the trace by taking into account a set of physical variables related to the vessel and the refractory material.
It is an object of the present invention to provide a fully automated solution to the problem of inspecting and repairing vessels, and thus, significantly reducing the need of human supervision at the time of repair. It is another object of the present invention to more efficiently read a laser cloud to generate a 3D geometry of the interior of a vessel. It is another object of the invention to minimize the waste of refractory material when applied to the interior walls of a vessel. It is another object of the invention to produce a 3D image (as opposed to 2xc2xdD) of the interior of a vessel to enable the precise spraying of the refractory material, thus saving time and eliminating the need to carry out the operation during the day.
With these and other objects, advantages and features of the invention that may become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and to the several drawings attached herein.